The present invention provides a lock system for a variable diameter rotor blade system, and more particularly to a lock system which reduces an impact force upon the rotor blade assembly.
A tilt rotor or tilt wing aircraft typically employs a pair of rotor systems which are pivotable such that the rotors may assume a vertical or horizontal orientation. In a horizontal orientation (i.e., horizontal rotor plane), the aircraft is capable of hovering flight, while in a vertical orientation (i.e., vertical rotor plane), the aircraft is propelled in the same manner as conventional propeller-driven fixed-wing aircraft.
Variable Diameter Rotor (VDR) systems provide distinct advantages. When the plane of the rotor is oriented horizontally, the rotor diameter is enlarged for improved hovering efficiency and, when oriented vertically, the rotor diameter is reduced for improved propulsive efficiency. A VDR blade assembly typically provides an outboard blade segment configured to telescope over a torque tube member. A retraction/extension mechanism is selectively driven to extend and retract the outer blade segment. Controlling the extension and/or retraction of the outboard blade segment relative to the torque tube thereby varies the rotor diameter.
It is known to provide a lock system to provide fail-safe retention of the outboard blade segment to prevent full unintentional extension. However, during unintentional extension of the outboard blade section, the lock system may exert an undesirable impact load upon the rotor blade assembly.
Accordingly, it is desirable to provide a VDR lock system which assures the fail safe retention of the outboard blade section while minimizing negative impact load upon the VDR system.
A VDR blade system includes a plurality of variable diameter rotor blade assemblies which include an inboard rotor blade section or torque tube and an outboard rotor blade section which telescopes relative to the torque tube. Each VDR blade assembly includes a blade lock system according to the present invention which assures retention of the outboard blade section.
A set of blade pins are rigidly mounted into the outboard blade section and a set of mount pins are rigidly mounted to the mount assembly. A resilient bushing at least partially surrounds each pin to provide high-energy absorption, impact resistance and low compressive modules. An engagement member rotatably extends from each mount pin to selectively engage each respective blade pin to provide fail-safe retention of the outboard blade section.
During VDR rotor system operation, should the outboard rotor blade section become free, centrifugal force will cause the outboard rotor blade section to rapidly telescope radially outward over the torque tube. As the engagement member is aligned with its respective blade pin in the locked position full extension of the outboard rotor blade section will be prevented. The lock system, however, receives an impact force as the outboard blade section is decelerated. The bushings act as a series of springs to reduce the deceleration rate of the outboard rotor blade section. The lock system thus assures the fail safe retention of the outboard blade section while minimizing the impact force experienced by the VDR system.